The National Transportation Safety Board (NTSB) has begun the long process of determining what went wrong on Saturday when Asiana Airlines Flight 214 crashed upon landing at San Francisco International Airport, killing two people and injuring 182.

The NTSB’s “Go Team” assembled early in the morning on Sunday to start the first part of its investigation into the cause behind the devastating crash. Nothing — including pilot error — has been ruled out, according to investigators. Both black boxes were recovered and sent to the NTSB lab in Washington for analysis.

NTSB chairman Deborah Hersman said in a press conference on Sunday afternoon that the flight recorder showed that the jetliner attempted to abort its landing and come around for another try 1.5 seconds before it crashed at the San Francisco airport. The recorder also showed that the plane was flying too slowly as it approached the airport — well below the target landing speed of 137 knots (or 157 mph), although Hersman wouldn’t specify how fast the plane was moving — triggering a warning that the jetliner could stall. There was an increase in speed several seconds before the crash.

Asiana spokeswoman Lee Hyomin said that the pilot who had the controls during landing, Lee Gang-guk, had nearly 10,000 hours flying other planes but only 43 in the 777. The pilot was attempting his first landing of the 777 at the San Francisco airport on Saturday.

Three other pilots were on the plane, taking turns on the controls — all with more than 10,000 hours of flying experience. Lee Jeong-min, who had about 12,390 hours of flying experience, including 3,220 hours on the 777, was the deputy pilot, tasked with helping Lee Gang-guk get accustomed to the 777, according to Asiana Airlines.

Despite these revelations about the pilots’ experience, Hersman was hesitant to say that pilot error was the cause of the crash. “We know that there’s different levels of experience,” she told TODAY on Monday morning. “We need to understand what was going on between these two crew members at the time.”

Hersman told CNN on Saturday that the internal damage to the plane is “really striking,” and investigators were thankful there weren’t more deaths.

Yoon Young-doo, president of Asiana Airlines, said in a press conference on Sunday that the company believes there was no engine defect.

While details regarding the plane’s landing have yet to be confirmed, video and flight-tracking software show that the tail of the aircraft slammed into the edge of the runway first and broke off, sending the fuselage skidding on its belly, where it stopped just left of the runway and erupted in a ball of flame and smoke. The Daily Beast has a detailed report of the path and subsequent destruction of the plane after it landed, but all indications are that the aircraft was intact when it reached the runway.

Aviation expert and former pilot Jim Tilmon told CNN that it appeared that the pilot came in too low and pulled up too late. “For whatever reason, the pilot did not have enough power available to correct the rate of descent that brought him into contact with the ground before he wanted to be there,” Tilmon said.

According to a Federal Aviation Administration bulletin, airport technology called the instrument landing system, which helps pilots correctly approach the runway, was not operating at the time of the crash. However, Kevin Hiatt, chief executive of the Flight Safety Foundation, told NBC News that airports commonly take this system off-line for maintenance on clear days. Indeed, San Francisco had ideal flying conditions on Saturday.

NBC News says the pilot did not make a distress call before landing. Audio recording of the pilot’s conversation with the flight tower confirms this.

Asiana officials say the pilot was a veteran, who has been flying since 1996. Hersman said they hope to interview the aircraft’s crew within the next few days. They will be evaluated by a special team with the NTSB to determine whether a range of factors may have affected their performances — from fatigue to depth of experience.

Many experts are speculating if the cause of Saturday’s crash was similar to the incident with British Airways Flight 38 — also a 777 — which landed short of the runway at London’s Heathrow Airport in January 2008. That investigation concluded that the hard landing was caused by ice that had gathered in the fuel system of that plane’s Rolls-Royce engine. But Larry Rooney, veteran pilot, NTSB-trained accident investigator and executive vice president of the Coalition of Airline Pilots Association, was cautious to link the two.

“One of the things they taught us in accident school is to never fall in love with a theory, the thing that you think [is the cause] at the onset might not be,” Rooney tells TIME, adding that even the same model of plane could have one of several types of engines manufactured by different companies. And at this point, only the Rolls-Royce engine has been known to have an issue with fuel icing.

But if it wasn’t ice, what did cause a seemingly normal flight to turn deadly? Investigators hope that the data they uncover from the black boxes, in correlation with interviews with the crew, will help them determine what happened so that they can prevent similar incidents in the future.